In a field to hearing aids, a number of hearing aids with wireless communication functions are proposed, such as a function of establishing communication with a device that controls a sound volume of the hearing aid (e.g., Patent Document 1) and a function of performing signal processing to sound by establishing communication between right and left hearing aids in order to help a user to recognize a direction of a sound source (e.g., Patent Document 2).
A technique in relation to an antenna incorporated in a hearing aid is proposed as described, e.g., in Patent Document 3, in which an L-shaped or a coil-shaped antenna is formed by a conductive film in a hearing aid housing to be fit behind the ear, whereby a space for the antenna on a substrate can be dispensed with.
As an antenna of a wireless device used while fitted to the ear other than the hearing aid, a configuration of an antenna for an FM radio wave which is mounted to a behind-the-ear transceiver as is described, e.g., in Patent Document 4. In the antenna, a transceiver is held by an ear using a soft, slightly-flexible ear holding member. An antenna is arranged to protrude from a casing so as to extend from the ear toward the zenith. A microphone protrudes from the casing so as to be situated near a mouth. A printed board having an electronic circuit for wireless transceiving operation, a speaker oriented an ear face, a battery, etc. are disposed in the casing.
According to the configuration, the transceiver is used as a handset of a telephone set not shown. The transceiver receives an FM radio wave transmitted from the telephone set (a main phone) by the antenna and reproduces an audio signal, and the audio signal is output from the speaker near the ear. Speech sound picked up by the microphone can be converted into an FM radio wave, and the radio wave can be transmitted from the antenna to the telephone set (the main phone).
As a built-in antenna of a wireless device used while fitted behind the ear, a configuration of a behind-the-ear cordless earphone is described, e.g., in Patent Document 5. In the behind-the-ear cordless earphone, an ear hanger used for fitting a behind-the-ear cordless earphone to an ear is joined to the casing by way of a shaft and a joint. In a state where the behind-the-ear cordless earphone is fitted to the ear, a speaker becomes situated near the ear, and the microphone becomes situated near the mouth. An interior of the ear hanger is formed from a flexible metallic material, and an exterior of the ear hanger is coated with one layer of elastic substance. The metallic material in the ear hanger is used as a receiving antenna. According to the configuration, the antenna is built inside.
Incidentally, users of hearing aids have a desire to clearly hear sounds while watching a TV, etc. The desire can be fulfilled by establishing wireless communication between a TV set and the hearing aid and receiving a sound signal of the TV by the hearing aid. The TV set lies in a line of sight of the user of the hearing aid when the user watches a TV program. For this reason, the directivity of the antenna mounted to the hearing aid is desired to be oriented toward the line of sight when the user is wearing the hearing aid.    Patent Document 1: JP-A-2000-83297    Patent Document 2: JP-A-2002-504794    Patent Document 3: JP-A-2005-304038    Patent Document 4: JP-A-2004-361910 (FIG. 8)    Patent Document 5: JP-U-3078858 (FIG. 3)